Touch pads in general are described in e.g. U.S. Pat. Nos. 4,346,376, 4,484,179, 4,688,933, 5,945,981, 6,538,644, 5,679,930, 4,710,760, 4,484,179, 5,484,966, 6,172,667, 5,065,185, and 6,122,394, US 2003/0048257 and 2003/0052257, as well as JP 63143862, 08075659, and 08149515.